Ответ:

1. \((9.2-3.8):0.9+2.5\cdot4=5.4:0.9+10=6+10=16\).

2. \(\left(3\frac{1}{4}+2\frac{1}{4}\right)\cdot\frac{2}{5}-\frac{1}{10}=5\frac{1}{2}\cdot\frac{2}{5}-\frac{1}{10}=\frac{11}{2}\cdot\frac{2}{5}-\frac{1}{10}=\frac{11}{5}-\frac{1}{10}=\frac{22}{10}-\frac{1}{10}=\frac{21}{10}=2\frac{1}{10}\).

3. \(18:(3.6-1.8)+4.2\cdot0.5=18:1.8+2.1=10+2.1=12.1\).

4. \(\left(\frac{8}{12}-\frac{1}{4}\right):\frac{1}{3}+1\frac{1}{2}=\left(\frac{2}{3}-\frac{1}{4}\right):\frac{1}{3}+1\frac{1}{2}=\frac{5}{12}\cdot3+\frac{3}{2}=\frac{5}{4}+\frac{6}{4}=\frac{11}{4}=2\frac{3}{4}\).

Ответ: 1) 16; 2) 2 1/10; 3) 12,1; 4) 2 3/4.